The present invention relates to machine tools and more particularly to a transporting and positioning device for tool magazine of a bridge type machine tool with improved characteristics.
A conventional machine tool of bridge type is shown in FIG. 1 wherein a spindle 1 is provided adjacent a side of a cross-rail 2. The spindle 1 is able to move along a Y axis with respect to the cross-rail 2 and a Z axis with respect to itself. A table 3 is able to move along an X axis. With such three-axis movement, the machine tool can work on a work piece (not shown). Two columns 4 at both ends of the cross-rail 2 do not interfere with the movement of the spindle 1 along the Y axis. Hence, a tool magazine 5 can be provided adjacent one of the columns 4. The spindle 1 can move to a position above the tool magazine 5 for tool change.
Another conventional bridge type machine tool is shown in FIG. 2 wherein a spindle 6 is provided on a cross-rail 7 and is moveable along a Y axis defined by the cross-rail 7 and along a Z axis with respect to itself. A table 8 is able to move along an X axis. A travel distance of the spindle 6 does not enable it to access a tool magazine since the movement of the spindle 6 is defined in the cross-rail 7. Once the tool magazine is disposed in the travel distance of the spindle 6 it will interfere with a normal operation of the spindle 6. A solution to this problem is to dig an opening in one of columns 9 for forming a tool magazine 10 therein. In a tool change operation, a cylinder is activated to push the tool magazine 10 to a position within the travel distance of the spindle 6. Next, the spindle 6 is activated to move to a position above the tool magazine 10 for tool change. However, the prior art suffered from several disadvantages. For example, the opening in the column 9 will adversely affect a structural strength of the column 9. Further, the number of tools contained in the tool magazine 10 is limited due to a narrow space in the opening. A prolonging of the length of the cross-rail 7 can decrease a harmonic frequency of the machine tool, resulting in a lower rigidity of the whole construction. A proposal is to form the tool magazine 10 in an outside position rather than in the column 9. However, an additional cylinder is required to push the tool magazine 10 to a position within the travel distance of the spindle 6. Such cylinder is typically not precise in positioning and lacks moving stability. Hence, it is not reliable. An additional servo driving axis without the above drawback of the cylinder can be used to push the tool magazine 10. However, it can significantly increase a manufacturing cost. Hence, a need for improvement exists.
It is therefore an object of the present invention to provide a transporting and positioning device for tool magazine of a machine tool. The transporting and positioning device is activated by a servo driving system of the machine tool without the installation of an additional drive device. By utilizing the present invention, it is possible of effecting a quick, high precision positioning of the tool magazine and reducing the manufacturing and maintenance costs.
In one aspect of the present invention, there is provided a machine tool comprising, in combination two side columns; a cross-rail interconnecting the columns, the cross-rail having a lengthwise channel; a spindle moveable along the channel and along a lengthwise direction of itself, the spindle having a changeable element at its open end; a moveable table under the cross-rail; a servo driving system below the table; a magazine containing a plurality of elements; and a transporting and positioning device including a plate at a side of one of the columns, a pair of parallel guide-ways on the plate, a sliding seat mounted on the guide-ways for supporting the magazine thereon, a drive mechanism including a cylinder on a side of the seat, a positioning shaft, a connection block adjacent one side of the plate by a predetermined distance, the connection block including a top hole and being fixed to the table, and a second cylinder having a second positioning shaft; wherein in an operating state of the machine tool, the second positioning shaft is actuated by the second cylinder to project an adjustable distance through the plate to urge against the seat for fastening the seat and the tool magazine; and in a tool change, slide the seat along the guide-ways by activating the cylinder until the magazine is below the cross-rail, activate the servo driving system to drive both the table and the connection block to move along a predetermined direction until the hole is aligned with the positioning shaft, drive the positioning shaft into the hole for fastening, activate the spindle to move along the channel until the spindle is aligned with the magazine and within an operable distance so as to change the element of the spindle with one of the elements of the magazine.
In another aspect of the present invention, each of the element of the spindle and the elements of the magazine is a tool.
In still another aspect of the present invention, each of the element of the spindle and the elements of the magazine is an attachment head.
In a further aspect of the present invention, there is provided an EDM comprising, in combination: two side columns; a cross-rail interconnecting the columns, the cross-rail having a lengthwise channel; a ram moveable along the channel and along a lengthwise direction of itself, the ram having a changeable tool at its open end; a moveable table under the cross-rail; a servo driving system below the table; a magazine containing a plurality of tools; and a transporting and positioning device including a plate at a side of one of the columns, a pair of parallel guide-ways on the plate, a sliding seat mounted on the guide-ways for supporting the magazine thereon, a drive mechanism including a cylinder on a side of the seat, a positioning shaft, a connection block adjacent one side of the plate by a predetermined distance, the connection block including a top hole and being fixed to the table, and a second cylinder having a second positioning shaft; wherein in an operating state of the machine tool, the second positioning shaft is actuated by the second cylinder to project an adjustable distance through the plate to urge against the seat for fastening the seat and the tool magazine; and in a tool change, slide the seat along the guide-ways by activating the cylinder until the magazine is below the cross-rail, activate the servo driving system to drive both the table and the connection block to move along a predetermined direction until the hole is aligned with the positioning shaft, drive the positioning shaft into the hole for fastening, activate the ram to move along the channel until the ram is aligned with the magazine and within an operable distance so as to change the tool of the ram with one of the tools of the magazine.